Prior to the present invention, no means has been found to provide simultaneous high and low pressure pulsating streams without the use of separate apparatus to provide each pulsating stream. To provide two separate apparatuses to provide two pulsating output streams at different pressures is expensive and may create space requirements which are impractical for particular applications.
U.S. Pat. No. 2,508,298 to Saari has a fluid pressure intensifier using a pair of pistons and piston rods, respectively. Flow is controlled by spool valves. This device provides a single higher pressure fluid output from a single fluid input. On the reverse half cycle of each piston, fluid is discharged through a drain at low pressure.
U.S. Pat. No. 3,086,470 to Skipor, et al. has a pump motor combination attached by a tubular connecting rod with a timing rod affixed to its ends which controls a valve unit. This device provides a single pulsating output at high pressure wherein low pressure fluid is discharged on the opposite half of the cycle.
U.S. Pat. No. 3,174,409 to Hill discloses a pump driven by gas and having a gas operated control valve to reciprocate a gas piston. This piston movement provides a pulsating fluid discharge which may be greater than the fluid line pressure.
U.S. Pat. No. 3,489,100 discloses a pump driven by gas or manually or both to reciprocate a gas piston. This also provides a pulsating fluid discharge which may be greater than the fluid line pressure.
U.S. Pat. No. 3,963,383 to Hill discloses an improvement of U.S. Pat. No. 3,174,409 which includes a spring means for moving the gas piston in one direction of its cycle.
U.S. Pat. No. 4,163,632 to Hinchman, et al. discloses a hydraulic pump mechanically connected to a fluid motor control valve. In one embodiment, the device includes a double-acting motor and pumps and a slide control valve connected to the piston of the motor. The slide valve is controlled by a rod which strikes pins as the motor piston moves reciprocally. This causes the valve to be shifted mechanically at the end of each stroke to reverse the direction of the piston. One fluid is used for operating the motor and the pump pumps a second fluid.
U.S. Pat. No. 4,793,153 to Hembree, et al. discloses a first low pressure liquid entering the cylinders of a pump and exhausted at a higher pressure by a second high pressure liquid which drives the pump. A third liquid drives the motor and exhausts in a vapor/liquid mixture which helps drive the motor as the vapor expands. Electrical switches are provided at the end of the travel of the pump pistons causing valves to be electrically switched from a first to a second position and back again. Energy is transferred from the second and third liquids to the first liquid to create the high pressure. The piston areas are unequal in the motor and only one high pressure outlet is provided. There is no concept of providing both pulsating high and low pressure outputs.